Bias current supply circuit and amplification circuit

ABSTRACT

A bias current supply circuit according to an embodiment of the invention includes a first transistor and a second transistor which form two emitter followers cooperating to supply a base bias current of a bipolar transistor for signal amplification, a normal temperature characteristic circuit which has normal temperature characteristics increasing an amount of current supply with increasing temperature and supplies a base current to the first bipolar transistor, and a reverse temperature characteristic circuit which has reverse temperature characteristics decreasing the amount of current supply with increasing temperature and supplies a base current to the second bipolar transistor.

CROSS REFERENCE TO RELATED APPLICATION

[0001] The subject application is related to subject matter disclosed inJapanese Patent Application No. 2003-066733 filed on Mar. 12, 2003 inJapan to which the subject application claims priority under ParisConvention and which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a bias current supply circuitand an amplification circuit including the bias current supply circuit.Particularly the invention relates to the high-efficiency, high-poweramplification circuit which is configured to use a bipolar transistorand operated by low power-supply voltage, and the bias current supplycircuit which is added to the amplification circuit.

[0004] 2. Related Background Art

[0005] In the high-efficiency, high-power amplification circuit which isconfigured to use the bipolar transistor and operated by the lowpower-supply voltage, since a collector current is greatly influenced bya fluctuation in temperature, a base bias current is supplied by acurrent mirror circuit which is configured to use a diode-connectedbipolar transistor.

[0006]FIG. 1 shows a circuit diagram of a first example of theconventional current mirror type base bias current supply circuits.

[0007] The current mirror circuit shown in FIG. 1 is the current mirrortype base bias current supply circuit having the simplest configuration.The current mirror circuit includes a resistor R and a diode-connectedbipolar transistor Q which are connected in series between a controlpotential node to which control voltage V_(con) is supplied and a groundpotential node, and the base bias current is supplied from a connectionnode OUT between the resistor R and a collector of the transistor Q.

[0008] The high-efficiency amplifier having a wide output dynamic rangeand linearity of gain can be realized by setting a bias condition toclass B to cut passage of idle current. However, in actual fact, sincestrain caused by a fluctuation in gain is increased by non-linearity ofmutual conductance of an element, the linearity of the gain ismaintained in the wide output dynamic range by setting the biascondition to class AB in which the idle current passes through theamplifier to a certain extent.

[0009] In the class AB amplification circuit configured to use thebipolar transistor, since average collector current is increasedaccording to an increase in output level, it is necessary that a biascircuit sufficiently supplies an increased amount in average basecurrent according to the increase in average collector current. However,in the current mirror circuit including the diode-connected bipolartransistor shown in FIG. 1, the sufficient current can not be supplied.

[0010] Therefore, the current mirror circuit which supplies the basecurrent through an emitter follower circuit is widely used in order todecrease output impedance.

[0011]FIG. 2 shows the circuit diagram of a second example of theconventional current mirror type base bias current supply circuits.

[0012] The conventional current mirror type base bias current supplycircuit shown in FIG. 2 includes a resistor R1 and diode-connectedbipolar transistors Q2 and Q1 which are sequentially connected in seriesbetween the control potential node to which the control voltage V_(con)is supplied and the ground potential node, a bipolar transistor Q3 inwhich the collector is connected to a power supply potential node towhich power supply voltage V_(cc) is supplied and a base is connected toa collector of the transistor Q2, and a resistor R2 which is connectedbetween an emitter of the transistor Q3 and the ground potential node.The base bias current is supplied from the connection node OUT betweenthe emitter of the transistor Q3 and the resistor R2.

[0013] However, since the conventional current mirror type base biascurrent supply circuit shown in FIG. 2 has the configuration in whichthe bipolar transistors are connected in two-stage series, unless thecontrol voltage V_(con) is sufficiently increased more than doublevoltage of on-voltage Vbeon of the transistor, it is impossible tomaintain compensation for a fluctuation in bias current to temperaturechange, in which responsiveness is required.

[0014] However, in a system such as a cellular phone in which thecontrol voltage is low, that the control voltage V_(con) is increased iscontrary to a flow of technical advance, so that there is generated aproblem. Particularly, in the system in which linear operation isrequired in the wide output dynamic range like a CDMA communicationsystem, a fluctuation in idle current caused by the temperature change,which is largely affected during low output, becomes the problem.

[0015] For the purpose of a countermeasure against the above problem, acomplex type bias current supply circuit in which the transistor turnedon by one-stage on-voltage Vbeon is added has been proposed.

[0016]FIG. 3 shows the circuit diagram of a third example of theconventional current mirror type base bias current supply circuits.

[0017] The conventional current mirror type base bias current supplycircuit shown in FIG. 3 includes a resistor R1 and diode-connectedbipolar transistors Q2 and Q1 which are sequentially connected in seriesbetween the control potential node to which the control voltage V_(con)is supplied and the ground potential node, a bipolar transistor Q4 inwhich the collector is connected to the power supply potential node towhich the power supply voltage V_(cc) is supplied and the base isconnected to the collector of the transistor Q2, a resistor R2 which isconnected between the control potential node and the emitter of thetransistor Q4, and a diode-connected bipolar transistor Q3 which isconnected between the emitter of the transistor Q4 and the groundpotential node. The base bias current is supplied from the connectionnode between the emitter of the transistor Q4 and the collector of thetransistor Q3.

[0018] The base bias current is supplied to the base of a bipolartransistor RFTr for RF signal amplification through a choke inductor L.The transistor RFTr is connected between the power supply potential nodeand the ground potential node, an input RF signal RF_(in) is inputted tothe base of the transistor RFTr through a capacitor C, and an output RFsignal RF_(out) is outputted from the collector of the transistor RFTr.

[0019]FIG. 4 is a graph showing temperature characteristics of thecollector bias current of the bipolar transistor for RF signalamplification to the control voltage V_(con) in the case where theconventional current mirror type base bias current supply circuit shownin FIG. 3 is used. Specifically, the graphs T1, T2, and T3 show thetemperature characteristics at ambient temperatures 90° C., 30° C., and−30° C. respectively.

[0020] In the case where the conventional current mirror type base biascurrent supply circuit shown in FIG. 3 is used, assuming that thecontrol voltage V_(con) is set to, e.g. the voltage as low as 2.8V, thecollector bias currents of the bipolar transistor for RF signalamplification become 27 mA, 35 mA, and 45 mA at the ambient temperatures−30° C., 30° C., and 90° C. respectively. This fluctuation range isdecreased and improved, compared with the case in which the conventionalcurrent mirror type base bias current supply circuit shown in FIG. 2 isused.

[0021] However, in the case where the conventional current mirror typebase bias current supply circuit shown in FIG. 3 is used, in fact thefluctuation range is not sufficiently decreased, because it is necessarythat the sufficient current passes through the transistor Q4 in order todecrease the output impedance.

[0022] Further, since the RF signal is leaked into the bias currentsupply circuit due to the low output impedance of the bias currentsupply circuit, as shown in FIG. 3, the choke inductor L arrangedbetween the output node of the bias current supply circuit and thebipolar transistor RFTr for RF signal amplification is essential forprevention of the RF signal.

SUMMARY OF THE INVENTION

[0023] According to a basic configuration of a bias current supplycircuit of a first embodiment of the invention, there is provided with abias current supply circuit comprising:

[0024] a first bipolar transistor and a second bipolar transistor whichform two emitter followers cooperating to supply a base bias current ofa bipolar transistor for signal amplification;

[0025] a normal temperature characteristic circuit which has normaltemperature characteristics increasing an amount of current supply withincreasing temperature and supplies a base current to the first bipolartransistor; and

[0026] a reverse temperature characteristic circuit which has reversetemperature characteristics decreasing the amount of current supply withincreasing temperature and supplies a base current to the second bipolartransistor.

[0027] According to another aspect of the basic configuration of thebias current supply circuit of the first embodiment of the invention,there is provided with a bias current supply circuit comprising:

[0028] a first bipolar transistor and a resistor which are sequentiallyconnected in series between a power supply potential node and a groundpotential node;

[0029] a second bipolar transistor which is connected in parallel withthe first bipolar transistor;

[0030] a normal temperature characteristic circuit which has normaltemperature characteristics increasing an amount of current supply withincreasing temperature and is operated by supply of a control voltage tocontrol a base current supplied to the first bipolar transistor; and

[0031] a reverse temperature characteristic circuit which has reversetemperature characteristics decreasing the amount of current supply withincreasing temperature and is operated by the supply of the controlvoltage to control a base current supplied to the second bipolartransistor,

[0032] wherein a base bias current of a bipolar transistor for signalamplification is supplied from emitters of the first and second bipolartransistors which are commonly connected.

[0033] According to a specific configuration of the bias current supplycircuit of the first embodiment of the invention, there is provided-witha bias current supply circuit comprising:

[0034] a first bipolar transistor and a second bipolar transistor whichare sequentially connected in series between a power supply potentialnode and a ground potential node;

[0035] a third bipolar transistor and a first diode-connected bipolartransistor which are sequentially connected in series between the powersupply potential node and the ground potential node;

[0036] a first resistor which is connected between a control potentialnode and a base of the first bipolar transistor;

[0037] a fourth bipolar transistor in which a collector is connected tothe base of the first bipolar transistor, a base is commonly connectedto bases of the second bipolar transistor and the first diode-connectedbipolar transistor, and an emitter is connected to the ground potentialnode;

[0038] a fifth bipolar transistor which is connected between the powersupply potential node and an emitter of the first bipolar transistor;

[0039] a second resistor which is connected between the controlpotential node and a base of the fifth bipolar transistor;

[0040] a third resistor and a sixth bipolar transistor which aresequentially connected in series between the base of the fifth bipolartransistor and the ground potential node;

[0041] a seventh bipolar transistor which is connected between the powersupply potential node and a base of the sixth bipolar transistor;

[0042] a fourth resistor which is connected between an emitter of theseventh bipolar transistor and the ground potential node;

[0043] a fifth resistor which is connected between the control potentialnode and a base of the seventh bipolar transistor; and

[0044] a second diode-connected bipolar transistor and a thirddiode-connected bipolar transistor which are sequentially connected inseries between the base of the seventh bipolar transistor and the groundpotential node.

[0045] According to a basic configuration of a bias current supplycircuit of a second embodiment of the invention, there is provided witha bias current supply circuit comprising:

[0046] a first bipolar transistor which forms an emitter followersupplying a base bias current of a bipolar transistor for signalamplification;

[0047] a second bipolar transistor which is connected in series to thefirst bipolar transistor;

[0048] a normal temperature characteristic circuit which has normaltemperature characteristics increasing an amount of current supply withincreasing temperature and supplies a base current to the first bipolartransistor; and

[0049] a bias current compensation circuit which has the normaltemperature characteristics increasing the amount of current supply withincreasing temperature and suppresses an increase in the base biascurrent with increasing ambient temperature by supplying a base currentto the second bipolar transistor to pass a part of the base bias currentsupplied from an emitter of the first bipolar transistor through thesecond bipolar transistor.

[0050] According to another aspect of the basic configuration of thebias current supply circuit of the first embodiment of the invention,there is provided with a bias current supply circuit comprising:

[0051] a first bipolar transistor and a second bipolar transistor whichare sequentially connected in series between a power supply potentialnode and a ground potential node;

[0052] a normal temperature characteristic circuit which has normaltemperature characteristics increasing an amount of current supply withincreasing temperature and is operated by supply of a control voltage tocontrol a base current supplied to the first bipolar transistor; and

[0053] a bias current compensation circuit which has the normaltemperature characteristics increasing the amount of current supply withincreasing temperature, the bias current compensation circuitcontrolling a base bias current of a bipolar transistor for signalamplification, which is supplied from an emitter of the first bipolartransistor, in such a manner that the bias current compensation circuitis operated by supply of the control voltage to control a base currentsupplied to the second bipolar transistor.

[0054] According to a specific configuration of a bias current supplycircuit of the embodiment of the invention, there is provided with abias current supply circuit comprising:

[0055] a first bipolar transistor and a second bipolar transistor whichare sequentially connected in series between a power supply potentialnode and a ground potential node;

[0056] a third bipolar transistor and a first diode-connected bipolartransistor which are sequentially connected in series between the powersupply potential node and the ground potential node;

[0057] a first resistor which is connected between a control potentialnode and a base of the first bipolar transistor;

[0058] a fourth bipolar transistor in which a collector is connected tothe base of the first bipolar transistor, a base is commonly connectedto bases of the second bipolar transistor and the first diode-connectedbipolar transistor, and an emitter is connected to the ground potentialnode;

[0059] a fifth bipolar transistor which is connected between an emitterof the first bipolar transistor and the ground potential node;

[0060] a sixth bipolar transistor in which a collector is connected tothe power supply potential node and an emitter is connected to a base ofthe fifth bipolar transistor;

[0061] a second resistor which is connected between an emitter of thesixth bipolar transistor and the ground potential node;

[0062] a third resistor which is connected between the control potentialnode and a base of the sixth bipolar transistor; and

[0063] a fourth resistor, a second diode-connected bipolar transistor,and a third diode-connected bipolar transistor which are sequentiallyconnected in series between the base of the sixth bipolar transistor andthe ground potential node.

[0064] According to a bias current supply circuit of a third embodimentof the invention, there is provided with a bias current supply circuitcomprising:

[0065] a first resistor and a first bipolar transistor which aresequentially connected in series between a control potential node and aground potential node;

[0066] a second bipolar transistor in which a collector is connected toa power supply potential node, a base is connected to a collector of thefirst bipolar transistor, and an emitter is connected to a base of thefirst bipolar transistor;

[0067] a second resistor which is connected between the emitter of thesecond bipolar transistor and the ground potential node;

[0068] a third bipolar transistor in which a collector is connected tothe power supply potential node, a base is commonly connected to thebase of the first bipolar transistor, and an emitter supplies a basebias current of a bipolar transistor for signal amplification;

[0069] a diode-connected bipolar transistor which is connected betweenthe emitter of the third bipolar transistor and the ground potentialnode; and

[0070] a third resistor which is connected between the control potentialnode and a connection node of the emitter of the third bipolartransistor and a collector of the diode-connected bipolar transistor.

[0071] According to a basic configuration of an amplification circuit ofa first embodiment of the invention, there is provided with anamplification circuit comprising:

[0072] a first bipolar transistor and a second bipolar transistor whichform two emitter followers cooperating to supply a base bias current ofa bipolar transistor for signal amplification;

[0073] a normal temperature characteristic circuit which has normaltemperature characteristics increasing an amount of current supply withincreasing temperature and supplies a base current to the first bipolartransistor;

[0074] a reverse temperature characteristic circuit which has reversetemperature characteristics decreasing the amount of current supply withincreasing temperature and supplies a base current to the second bipolartransistor; and

[0075] the bipolar transistor for signal amplification which isconnected between a power supply potential node and a ground potentialnode, a base of the bipolar transistor for signal amplification beingconnected to emitters of the first and second bipolar transistors, aninput signal being inputted to a base of the bipolar transistor forsignal amplification through a capacitor, an output signal beingoutputted from a collector of the bipolar transistor for signalamplification.

[0076] According to another aspect of the basic configuration of theamplification circuit of the first embodiment of the invention, there isprovided with an amplification circuit comprising:

[0077] a first bipolar transistor and a resistor which are sequentiallyconnected in series between a power supply potential node and a groundpotential node;

[0078] a second bipolar transistor which is connected in parallel withthe first bipolar transistor;

[0079] a normal temperature characteristic circuit which has normaltemperature characteristics increasing an amount of current supply withincreasing temperature and is operated by supply of a control voltage tocontrol a base current supplied to the first bipolar transistor;

[0080] a reverse temperature characteristic circuit which has reversetemperature characteristics decreasing the amount of current supply withincreasing temperature and is operated by the supply of the controlvoltage to control a base current supplied to the second bipolartransistor; and

[0081] a bipolar transistor for signal amplification which is connectedbetween the power supply potential node and the ground potential node, abase of the bipolar transistor for signal amplification being connectedto emitters of the first and second bipolar transistors, an input signalbeing inputted to a base of the bipolar transistor for signalamplification through a capacitor, an output signal being outputted froma collector of the bipolar transistor for signal amplification.

[0082] According to a specific configuration of an amplification circuitof a first embodiment of the invention, there is provided with anamplification circuit comprising:

[0083] a first bipolar transistor and a second bipolar transistor whichare sequentially connected in series between a power supply potentialnode and a ground potential node;

[0084] a third bipolar transistor and a first diode-connected bipolartransistor which are sequentially connected in series between the powersupply potential node and the ground potential node;

[0085] a first resistor which is connected between a control potentialnode and a base of the first bipolar transistor;

[0086] a fourth bipolar transistor in which a collector is connected tothe base of the first bipolar transistor, a base is commonly connectedto bases of the second bipolar transistor and the first diode-connectedbipolar transistor, and an emitter is connected to the ground potentialnode;

[0087] a fifth bipolar transistor which is connected between the powersupply potential node and an emitter of the first bipolar transistor;

[0088] a second resistor which is connected between the controlpotential node and a base of the fifth bipolar transistor;

[0089] a third resistor and a sixth bipolar transistor which aresequentially connected in series between the base of the fifth bipolartransistor and the ground potential node;

[0090] a seventh bipolar transistor which is connected between the powersupply potential node and a base of the sixth bipolar transistor;

[0091] a fourth resistor which is connected between an emitter of theseventh bipolar transistor and the ground potential node;

[0092] a fifth resistor which is connected between the control potentialnode and a base of the seventh bipolar transistor;

[0093] a second diode-connected bipolar transistor and a thirddiode-connected bipolar transistor which are sequentially connected inseries between the base of the seventh bipolar transistor and the groundpotential node; and

[0094] a bipolar transistor for signal amplification which is connectedbetween the power supply potential node and the ground potential node, abase of the bipolar transistor for signal amplification being connectedto the emitter of the first bipolar transistor and an emitter of thefifth bipolar transistor, an input signal being inputted to the base ofthe bipolar transistor for signal amplification through a capacitor, anoutput signal being outputted from an collector of the bipolartransistor for signal amplification.

[0095] According to a basic configuration of an amplification circuit ofa second embodiment of the invention, there is provided with anamplification circuit comprising:

[0096] a first bipolar transistor which forms an emitter followersupplying a base bias current of a bipolar transistor for signalamplification;

[0097] a second bipolar transistor which is connected in series to thefirst bipolar transistor;

[0098] a normal temperature characteristic circuit which has normaltemperature characteristics increasing an amount of current supply withincreasing temperature and supplies a base current to the first bipolartransistor;

[0099] a bias current compensation circuit which has the normaltemperature characteristics increasing the amount of current supply withincreasing temperature and suppresses an increase the the base biascurrent with increasing ambient temperature by supplying a base currentto the second bipolar transistor to pass a part of the base bias currentsupplied from an emitter of the first bipolar transistor through thesecond bipolar transistor; and

[0100] the bipolar transistor for signal amplification which isconnected between a power supply potential node and a ground potentialnode, a base of the bipolar transistor for signal amplification beingconnected to the emitter of the first bipolar transistor, an inputsignal being inputted to the base of the bipolar transistor for signalamplification through a capacitor, an output signal being outputted froma collector of the bipolar transistor for signal amplification.

[0101] According to another aspect of the basic configuration of theamplification circuit of the second embodiment of the invention, thereis provided with an amplification circuit comprising:

[0102] a first bipolar transistor and a second bipolar transistor whichare sequentially connected in series between a power supply potentialnode and a ground potential node;

[0103] a normal temperature characteristic circuit which has normaltemperature characteristics increasing an amount of current supply withincreasing temperature and is operated by supply of a control voltage tocontrol a base current supplied to the first bipolar transistor;

[0104] a bias current compensation circuit which has the normaltemperature characteristics increasing the amount of current supply withincreasing temperature, the bias current compensation circuitcontrolling a base bias current of a bipolar transistor for signalamplification, which is supplied from an emitter of the first bipolartransistor, in such a manner that the bias current compensation circuitis operated by supply of the control voltage to control a base currentsupplied to the second bipolar transistor; and

[0105] the bipolar transistor for signal amplification which isconnected between the power supply potential node and the groundpotential node, a base of the bipolar transistor for signalamplification being connected to the emitter of the first bipolartransistor, an input signal being inputted to the base of the bipolartransistor for signal amplification through a capacitor, an outputsignal being outputted from a collector of the bipolar transistor forsignal amplification.

[0106] According to a specific configuration of an amplification circuitof a third embodiment of the invention, there is provided with anamplification circuit comprising:

[0107] a first bipolar transistor and a second bipolar transistor whichare sequentially connected in series between a power supply potentialnode and a ground potential node;

[0108] a third bipolar transistor and a first diode-connected bipolartransistor which are sequentially connected in series between the powersupply potential node and the ground potential node;

[0109] a first resistor which is connected between a control potentialnode and a base of the first bipolar transistor;

[0110] a fourth bipolar transistor in which a collector is connected tothe base of the first bipolar transistor, a base is commonly connectedto bases of the second bipolar transistor and the first diode-connectedbipolar transistor, and an emitter is connected to the ground potentialnode;

[0111] a fifth bipolar transistor which is connected between an emitterof the first bipolar transistor and the ground potential node;

[0112] a sixth bipolar transistor in which a collector is connected tothe power supply potential node and an emitter is connected to a base ofthe fifth bipolar transistor;

[0113] a second resistor which is connected between an emitter of thesixth bipolar transistor and the ground potential node;

[0114] a third resistor which is connected between the control potentialnode and a base of the sixth bipolar transistor;

[0115] a fourth resistor, a second diode-connected bipolar transistor,and a third diode-connected bipolar transistor which are sequentiallyconnected in series between the base of the sixth bipolar transistor andthe ground potential node; and

[0116] a bipolar transistor for signal amplification which is connectedbetween the power supply potential node and the ground potential node, abase of the bipolar transistor for signal amplification being connectedto the emitter of the first bipolar transistor, an input signal beinginputted to the base of the bipolar transistor for signal amplificationthrough a capacitor, an output signal being outputted from a collectorof the bipolar transistor for signal amplification.

[0117] According to an amplification circuit of a third embodiment ofthe invention, there is provided with an amplification circuitcomprising:

[0118] a first resistor and a first bipolar transistor which aresequentially connected in series between a control potential node and aground potential node;

[0119] a second bipolar transistor in which a collector is connected toa power supply potential node, a base is connected to a collector of thefirst bipolar transistor, and an emitter is connected to a base of thefirst bipolar transistor;

[0120] a second resistor which is connected between the emitter of thesecond bipolar transistor and the ground potential node;

[0121] a third bipolar transistor in which a collector is connected tothe power supply potential node, a base is commonly connected to thebase of the first bipolar transistor, and an emitter supplies a basebias current of a bipolar transistor for signal amplification;

[0122] a diode-connected bipolar transistor which is connected betweenthe emitter of the third bipolar transistor and the ground potentialnode;

[0123] a third resistor which is connected between the control potentialnode and a connection node of the emitter of the third bipolartransistor and a collector of the diode-connected bipolar transistor;and

[0124] the bipolar transistor for signal amplification which isconnected between the power supply potential node and the groundpotential node, a base of the bipolar transistor for signalamplification being connected to the emitter of the third bipolartransistor, an input signal being inputted to the base of the bipolartransistor for signal amplification through a capacitor, an outputsignal being outputted from a collector of the bipolar transistor forsignal amplification.

BRIEF DESCRIPTION OF THE DRAWINGS

[0125]FIG. 1 is a circuit diagram of a first example of the conventionalcurrent mirror type base bias current supply circuits;

[0126]FIG. 2 is a circuit diagram of a second example of theconventional current mirror type base bias current supply circuits;

[0127]FIG. 3 is a circuit diagram of a third example of the conventionalcurrent mirror type base bias current supply circuits;

[0128]FIG. 4 is a graph showing temperature characteristics of acollector bias current of a bipolar transistor for RF signalamplification to control voltage V_(con) in the case where theconventional current mirror type base bias current supply circuit shownin FIG. 3 is used;

[0129]FIG. 5 is a circuit diagram showing a basic configuration of thebias current supply circuit and an amplification circuit according to afirst embodiment of the invention;

[0130]FIG. 6 is a circuit diagram showing an example of specificconfigurations of the bias current supply circuit and the amplificationcircuit according to the first embodiment of the invention;

[0131]FIG. 7 is a graph showing the temperature characteristics of thecollector bias current of the bipolar transistor for RF signalamplification to the control voltage V_(con) in the case where the biascurrent supply circuit according to the first embodiment of theinvention is used;

[0132]FIG. 8 is a graph showing the temperature characteristics of thecollector bias current of the bipolar transistor for RF signalamplification to the control voltage V_(con) in the case where only abias current supply circuit A in the bias current supply circuitaccording to the first embodiment of the invention is used;

[0133]FIG. 9 is a circuit diagram showing the basic configuration of thebias current supply circuit and the amplification circuit according to asecond embodiment of the invention;

[0134]FIG. 10 is a circuit diagram showing a specific example of thebias current supply circuits and the amplification circuits according tothe second embodiment of the invention;

[0135]FIG. 11 is a graph showing the temperature characteristics of thecollector bias current of the bipolar transistor for RF signalamplification to the control voltage V_(con) in the case where the biascurrent supply circuit according to the second embodiment of theinvention is used;

[0136]FIG. 12 is a circuit diagram showing the configuration of the biascurrent supply circuit and the amplification circuit according to athird embodiment of the invention;

[0137]FIG. 13 a graph showing the temperature characteristics of thecollector bias current of the bipolar transistor for RF signalamplification to the control voltage V_(con) in the case where the biascurrent supply circuit according to the third embodiment of theinvention is used; and

[0138]FIG. 14 is a circuit diagram showing the configuration of amodification of the bias current supply circuits and the amplificationcircuits according to the third embodiment of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0139] Embodiments of the bias current supply circuit and theamplification circuit of the invention will be described below referringto the accompanying drawings.

[0140]FIG. 5 is the circuit diagram showing a basic configuration of thebias current supply circuit and the amplification circuit according to afirst embodiment of the invention.

[0141] The bias current supply circuit according to the first embodimentof the invention includes a first bipolar transistor Q1 and a resistor Rwhich are sequentially connected in series between the power supplypotential node to which the power supply voltage V_(cc) is supplied andthe ground potential node, a second bipolar transistor Q2 which isconnected in parallel with the first bipolar transistor Q1, a normaltemperature characteristic circuit 1 which has normal temperaturecharacteristics increasing an amount of current supply with increasingtemperature and is operated by supply of the control voltage V_(con) tocontrol the base current supplied to the first bipolar transistor Q1,and a reverse temperature characteristic circuit 2 which has reversetemperature characteristics decreasing the amount of current supply withincreasing temperature and is operated by the supply of the controlvoltage V_(con) to control the base current supplied to the secondbipolar transistor Q2. The base bias current of the bipolar transistorRFTr for RF signal amplification is supplied from the connection nodebetween the first and second bipolar transistors Q1 and Q2 and theresistor R, i.e. the emitters of the first and second bipolartransistors Q1 and Q2 which are commonly connected.

[0142] The amplification circuit includes the bipolar transistor RFTrfor RF signal amplification which is connected between the power supplypotential node and the ground potential node. In the bipolar transistorRFTr for RF signal amplification, the base is connected to the emittersof the first and second bipolar transistors Q1 and Q2, the input RFsignal RF_(in) is inputted to the base through a capacitor C, and theoutput RF signal RF_(out) is outputted from the collector.

[0143] In the configuration shown in FIG. 5, a choke inductor L forpreventing the RF signal is inserted and connected between the base ofthe bipolar transistor RFTr for RF signal amplification and the emittersof the first and second bipolar transistors Q1 and Q2. However, it isarbitrary whether the choke inductor L is provided or not, and it isalso possible to remove the choke inductor L to cause short circuit.

[0144] That is to say, the bias current supply circuit according to thefirst embodiment of the invention includes the first and second bipolartransistors Q1 and Q2 which form the two emitter followers cooperatingto supply the base bias current of the bipolar transistor RFTr for RFsignal amplification, the normal temperature characteristic circuit 1which has the normal temperature characteristics increasing the amountof current supply with increasing temperature and supplies the basecurrent to the first bipolar transistor Q1, and the reverse temperaturecharacteristic circuit 2 which has the reverse temperaturecharacteristics decreasing the amount of current supply with increasingtemperature and supplies the base current to the second bipolartransistor Q2.

[0145] In the bias current supply circuit according to the firstembodiment of the invention, since the base current supplied from thenormal temperature characteristic circuit 1 to the first bipolartransistor Q1 is increased with increasing ambient temperature, whilethe emitter current of the first bipolar transistor Q1 is increased, thebase current supplied from the reverse temperature characteristiccircuit 2 to the second bipolar transistor Q2 is decreased. This allowsthe emitter current of the second bipolar transistor Q2 to be decreased.

[0146] On the contrary, since the base current supplied from the normaltemperature characteristic circuit 1 to the first bipolar transistor Q1is decreased with decreasing ambient temperature, while the emittercurrent of the first bipolar transistor Q1 is decreased, the basecurrent supplied from the reverse temperature characteristic circuit 2to the second bipolar transistor Q2 is increased. This allows theemitter current of the second bipolar transistor Q2 to be increased.

[0147] Accordingly, in the bipolar transistor RFTr for RF signalamplification whose base bias current is supplied by the cooperation ofthe two emitter followers formed by the first and second bipolartransistors Q1 and Q2, the fluctuation in base bias current caused bythe temperature change is cancelled. As a result, the fluctuation incollector bias current of the bipolar transistor RFTr for RF signalamplification, which is caused by the temperature change, is suppressedto the minimum.

[0148] As described later, because each of the temperaturecharacteristic circuit 1 and the reverse temperature characteristiccircuit 2 can be formed by combination of the bipolar transistors whichare turned on by the one-stage on-voltage Vbeon, the low-voltageoperation can be realized in the control voltage V_(con) of the biascurrent supply circuit according to the first embodiment of theinvention.

[0149]FIG. 6 is the circuit diagram showing an example of specificconfigurations of the bias current supply circuit and the amplificationcircuit according to the first embodiment of the invention.

[0150] The bias current supply circuit according to the first embodimentof the invention includes bipolar transistors Q1 and Q6 which aresequentially connected in series between the power supply potential nodeto which the power supply voltage V_(cc) is supplied and the groundpotential node, a bipolar transistor Q3 and a diode-connected bipolartransistor Q5 which are sequentially connected in series between thepower supply potential node and the ground potential node, a resistor R1which is connected between the control potential node to which thecontrol voltage V_(con) is supplied and the base of the transistor Q1, aresistor R2 which is connected between the base of the transistor Q3 andthe connection node of the base of the transistor Q1 and the resistorR1, a resistor R3 whose one end is connected to the base of thetransistor Q1, a bipolar transistor Q4 in which the collector isconnected to the other end of the resistor R3, the base is commonlyconnected to the bases of the transistors Q5 and Q6, and the emitter isconnected to the ground potential node, a bipolar transistor Q2 which isconnected between the power supply potential node and the emitter of thetransistor Q1, a resistor R4 which is connected between the controlpotential node and the base of the transistor Q2, a resistor R5 and abipolar transistor Q7 which are sequentially connected in series betweenthe base of the transistor Q2 and the ground potential node, a bipolartransistor Q8 which is connected between the power supply potential nodeand the base of the transistor Q7, a resistor R6 which is connectedbetween the emitter of the transistor Q8 and the ground potential node,a resistor R7 which is connected between the control potential node andthe base of the transistor Q8, and diode-connected bipolar transistorsQ9 and Q10 which are sequentially connected in series between the baseof the transistor Q8 and the ground potential node.

[0151] The amplification circuit includes the bipolar transistor RFTrfor RF signal amplification which is connected between the power supplypotential node and the ground potential node. In the bipolar transistorRFTr for RF signal amplification, the base is connected to the emittersof the bipolar transistors Q1 and Q2, the input RF signal RF_(in) isinputted to the base through a capacitor C, and the output RF signalRF_(out) is outputted from the collector.

[0152] In the configuration shown in FIG. 6, a choke inductor L forpreventing the RF signal is inserted and connected between the base ofthe bipolar transistor RFTr for RF signal amplification and the emittersof the bipolar transistors Q1 and Q2. However, it is arbitrary whetherthe choke inductor L is provided or not, and it is also possible toremove the choke inductor L to cause short circuit.

[0153] Further, the resistors R2 and R3 included in the bias currentsupply circuit according to the first embodiment of the invention shownin FIG. 6 also prevents the RF signal from leaking to the bias currentsupply circuit, it is arbitrary whether the resistors R2 and R3 areprovided or not, and it is also possible to remove the resistors R2 andR3 to cause short circuit respectively.

[0154] The circuit including the transistors Q3, Q4, Q5, and Q6 and theresistors R1, R2, and R3 corresponds to the normal temperaturecharacteristic circuit 1 shown in FIG. 5. The circuit including thetransistor Q1 which is of the emitter follower in addition to thecircuit including the transistors Q3, Q4, Q5, and Q6 and the resistorsR1, R2, and R3 forms a bias current supply circuit A having the usualtemperature characteristics.

[0155] Since the bias current supply circuit A has the usual temperaturecharacteristics, the transistor Q1 which is of the emitter followerincreases the base bias current supplied to the bipolar transistor RFTrfor RF signal amplification when the ambient temperature is increased,and the transistor Q1 decreases the base bias current when the ambienttemperature is decreased.

[0156] The transistors Q3, Q4, and Q5 form the current mirror circuitwhich sets a base potential of the transistor Q1. The transistor Q6 isone which sets a current value of the transistor Q1, and the basepotential of the transistor Q6 is supplied from the current mirrorcircuit including the transistors Q3, Q4, and Q5.

[0157] The resistor R1 sets the current value of the transistor Q3, andthe resistors R2 and R3 prevent the RF signal from leaking to the biascurrent supply circuit as described above.

[0158] The control voltage V_(con) determines the collector currents ofthe transistor Q1 and the bipolar transistor RFTr for RF signalamplification, which are supplied from the power supply potential node.

[0159] The circuit including the transistors Q7, Q8, Q9, and Q10 and theresistors R4, R5, R6, and R7 corresponds to the reverse temperaturecharacteristic circuit 2 shown in FIG. 5. The circuit including thetransistor Q2 which is of the emitter follower in addition to thecircuit including the transistors Q7, Q8, Q9, and Q10 and the resistorsR4, R5, R6, and R7 forms a bias current supply circuit B having thereverse temperature characteristics.

[0160] Since the bias current supply circuit B has the reversetemperature characteristics, the transistor Q2 which is of the emitterfollower decreases the base bias current supplied to the bipolartransistor RFTr for RF signal amplification when the ambient temperatureis increased, and the transistor Q1 increases the base bias current whenthe ambient temperature is decreased.

[0161] The base potential of the transistor Q2 is set by the collectorcurrent of the transistor Q7 and the resistor R7.

[0162] The circuit including the transistors Q8, Q9, and Q10 and theresistors R5 and R6 is one which sets the base potential of thetransistor Q7.

[0163] Since each of the bipolar transistors has the normal temperaturecharacteristics, while the collector current passing through thetransistor Q7 is increased with increasing ambient temperature, thecollector current is decreased with decreasing ambient temperature. Onthe other hand, the base potential of the transistor Q2 which is of theemitter follower is determined by voltage drop caused by the resistorR4. Accordingly, while the base potential of the transistor Q2 islargely decreased with increasing ambient temperature, the basepotential of the transistor Q2 is increased with decreasing ambienttemperature.

[0164] As a result, although the transistor Q2 which is of the emitterfollower supplies the sufficient base bias current to the bipolartransistor RFTr for RF signal amplification at a lower temperature, thetransistor Q2 cannot supply the base bias current to the bipolartransistor RFTr for RF signal amplification at a higher temperature.

[0165] Accordingly, in the bipolar transistor RFTr for RF signalamplification whose base bias current is supplied by the cooperation ofthe two emitter followers formed by the transistors Q1 and Q2, thefluctuation in base bias current caused by the temperature change iscancelled. This allows the fluctuation in collector bias current of thebipolar transistor RFTr for RF signal amplification, which is caused bythe temperature change, to be suppressed to the minimum.

[0166] Because each of the bias current supply circuit A and the biascurrent supply circuit B is formed by the combination of the bipolartransistors which are turned on by the one-stage on-voltage Vbeon, thelow-voltage operation can be realized in the control voltage V_(con) ofthe bias current supply circuit according to the first embodiment of theinvention.

[0167]FIG. 7 is the graph showing the temperature characteristics of thecollector bias current of the bipolar transistor for RF signalamplification to the control voltage V_(con) in the case where the biascurrent supply circuit according to the first embodiment of theinvention is used. FIG. 8 is the graph showing the temperaturecharacteristics of the collector bias current of the bipolar transistorfor RF signal amplification to the control voltage V_(con) in the casewhere only the bias current supply circuit A in the bias current supplycircuit according to the first embodiment of the invention is used. InFIGS. 7 and 8, the graphs T1, T2, and T3 show the temperaturecharacteristics at ambient temperatures 80° C., 30° C., and −20° C.respectively.

[0168] In the measurement of the temperature characteristics, an indiumgallium phosphide/gallium arsenide (InGaP/GaAs) heterojunction bipolartransistor is used as the bipolar transistor, and the forty eightbipolar transistors RFTr for RF signal amplification whose emitter sizeis 4×30 μm are used. In the bias current supply circuit, the eighttransistors Q1 whose emitter size is 4×30 μm are used, the sixtransistors Q2 whose emitter size is 4×30 μm are used, the twotransistors Q6 whose emitter size is 4×30 μm are used, and each one ofthe transistors Q3, Q4, Q5, Q7, Q8, Q9, and Q10 whose emitter size is4×10 μm is used.

[0169] With respect to a resistance value of each resistor, the resistorR1 is 600Ω, the resistor R2 is 1000Ω, the resistor R3 is 100Ω, theresistor R4 is 1000Ω, the resistor R5 is 600Ω, the resistor R6 is17000Ω, the resistor R7 is 2000Ω, and the resistor R8 is 200Ω.

[0170] The power supply voltage V_(cc) is 3.4V, and the controlvoltageV_(con) is variable in the range of 2.0V to 3.0V. However, eachof the above setting values is set on the assumption that the controlvoltage V_(con) is set to 2.8V.

[0171] As shown in the graphs of FIG. 7, in the case where the biascurrent supply circuit according to the first embodiment of theinvention is used, when the control voltage V_(con) is set to 2.8V, thecollector bias currents of the bipolar transistor for RF signalamplification are 46 mA, 42 mA, and 45 mA at the ambient temperaturesrespectively, and it is found that the collector bias current is changedlittle. Even if the control voltage V_(con) is fluctuated, it is foundthat the fluctuation in collector bias current of the bipolar transistorfor RF signal amplification is suppressed to a relatively small value.

[0172] On the other hand, as shown in the graphs of FIG. 8, in the casewhere only the bias current supply circuit A in the bias current supplycircuit according to the first embodiment of the invention is used, whenthe control voltage V_(con) is set to 2.8V, the collector bias currentsof the bipolar transistor for RF signal amplification are 75 mA, 52 mA,and 30 mA at the ambient temperatures respectively, and it is found thatthe collector bias current is largely changed.

[0173] That is to say, it is found that the use of the bias currentsupply circuit according to the first embodiment of the invention cansuppress the fluctuation in collector bias current of the bipolartransistor for RF signal amplification, which is caused by thetemperature change, to the minimum.

[0174]FIG. 9 is the circuit diagram showing the basic configuration ofthe bias current supply circuit and the amplification circuit accordingto a second embodiment of the invention.

[0175] The bias current supply circuit according to the secondembodiment of the invention includes a first bipolar transistors Q1 anda second bipolar transistor Q2 which are sequentially connected inseries between the power supply potential node to which the power supplyvoltage V_(cc) is supplied and the ground potential node, a normaltemperature characteristic circuit 1 which has the normal temperaturecharacteristics increasing the amount of current supply with increasingtemperature and is operated by the supply of the control voltage V_(con)to control the base current supplied to the first bipolar transistor Q1,and a bias current compensation circuit 3 which has the normaltemperature characteristics increasing the amount of current supply withincreasing temperature and controls the bias current supplied from theemitter of the first bipolar transistor Q1 in such a manner that thebias current compensation circuit is operated by the supply of thecontrol voltage V_(con) to control the base current supplied to thesecond bipolar transistor Q2. The base bias current of the bipolartransistor RFTr for RF signal amplification is supplied from theconnection node between the first and second bipolar transistors Q1 andQ2, i.e. the emitter of the first bipolar transistor Q1.

[0176] The amplification circuit includes the bipolar transistor RFTrfor RF signal amplification which is connected between the power supplypotential node and the ground potential node. In the bipolar transistorRFTr for RF signal amplification, the base is connected to the emitterof the first bipolar transistor Q1, the input RF signal RF_(in) isinputted to the base through a capacitor C, and the output RF signalRF_(out) is outputted from the collector.

[0177] In the configuration shown in FIG. 9, a choke inductor L forpreventing the RF signal is inserted and connected between the base ofthe bipolar transistor RFTr for RF signal amplification and the emittersof the first bipolar transistor Q1. However, it is arbitrary whether thechoke inductor L is provided or not, and it is also possible to removethe choke inductor L to cause short circuit.

[0178] That is to say, the bias current supply circuit according to thesecond embodiment of the invention includes the first bipolartransistors Q1 which forms the emitter follower supplying the base biascurrent of the bipolar transistor RFTr for RF signal amplification, thesecond bipolar transistor Q2 which is connected in series to the firstbipolar transistor Q1, the normal temperature characteristic circuit 1which has the normal temperature characteristics increasing the amountof current supply with increasing temperature and supplies the basecurrent to the first bipolar transistor Q1, and the bias currentcompensation circuit 3 which has the normal temperature characteristicsincreasing the amount of current supply with increasing temperature andsuppresses the increase in base bias current with increasing ambienttemperature by supplying the base current to the second bipolartransistor Q2 to passes a part of the base bias current supplied fromthe emitter of the first bipolar transistor Q1 through the secondbipolar transistor Q2.

[0179] In the bias current supply circuit according to the secondembodiment of the invention, since the base current supplied from thenormal temperature characteristic circuit 1 to the first bipolartransistor Q1 is increased with increasing ambient temperature, whilethe emitter current of the first bipolar transistor Q1 is increased, thebase current supplied from the bias current compensation circuit 3 tothe second bipolar transistor Q2 is also increased. As a result, thecurrent passing through the second bipolar transistor Q2 is increased inthe emitter current of the first bipolar transistor Q1, and the increasein bias current supplied from the emitter of the first bipolartransistor Q1 is suppressed.

[0180] On the contrary, since the base current supplied from the normaltemperature characteristic circuit 1 to the first bipolar transistor Q1is decreased with decreasing ambient temperature, while the emittercurrent of the first bipolar transistor Q1 is decreased, the basecurrent supplied from the bias current compensation circuit 3 to thesecond bipolar transistor Q2 is also decreased. As a result, the currentpassing through the second bipolar transistor Q2 is decreased in theemitter current of the first bipolar transistor Q1, a bias currentsuppression effect performed by the bias current compensation circuit 3and the second bipolar transistor Q2 substantially disappears, and themost part of the emitter current of the first bipolar transistor Q1 issupplied as the bias current.

[0181] Accordingly, in the bipolar transistor RFTr for RF signalamplification whose base bias current is supplied by the emitterfollower formed by the first bipolar transistor Q1, the fluctuation inbase bias current caused by the temperature change is cancelled. As aresult, the fluctuation in collector bias current of the bipolartransistor RFTr for RF signal amplification, which is caused by thetemperature change, is suppressed to the minimum.

[0182] As described later, because each of the temperaturecharacteristic circuit 1 and the bias current compensation circuit 3 canbe formed by the combination of the bipolar transistors which are turnedon by the one-stage on-voltage Vbeon, the low-voltage operation can berealized in the control voltage V_(con) of the bias current supplycircuit according to the second embodiment of the invention.

[0183]FIG. 10 is the circuit diagram showing a specific example of thebias current supply circuits and the amplification circuits according tothe second embodiment of the invention.

[0184] The bias current supply circuit according to the secondembodiment of the invention includes bipolar transistors Q1 and Q5 whichare sequentially connected in series between the power supply potentialnode to which the power supply voltage V_(cc) is supplied and the groundpotential node, a bipolar transistor Q2 and a diode-connected bipolartransistor Q4 which are sequentially connected in series between thepower supply potential node and the ground potential node, a resistor R1which is connected between the control potential node to which thecontrol voltage V_(con) is supplied and the base of the transistor Q1, aresistor R2 which is connected between the base of the transistor Q2 andthe connection node of the base of the transistor Q1 and the resistorR1, a resistor R3 whose one end is connected to the base of thetransistor Q1, a bipolar transistor Q3 in which the collector isconnected to the other end of the resistor R3, the base is commonlyconnected to the bases of the transistors Q4 and Q5, and the emitter isconnected to the ground potential node, a bipolar transistor Q6 which isconnected between the emitter of the transistor Q1 and the groundpotential node, a bipolar transistor Q7 in which the collector isconnected to the power supply potential node and the emitter isconnected to the base of the transistor Q6, a resistor R4 which isconnected between the emitter of the transistor Q7 and the groundpotential node, a resistor R5 which is connected between the controlpotential node and the base of the transistor Q7, and a resistor R6 anddiode-connected bipolar transistors Q8 and Q9 which are sequentiallyconnected in series between the base of the transistor Q7 and the groundpotential node.

[0185] The amplification circuit includes the bipolar transistor RFTrfor RF signal amplification which is connected between the power supplypotential node and the ground potential node. In the bipolar transistorRFTr for RF signal amplification, the base is connected to the emitterof the bipolar transistor Q1, the input RF signal RF_(in) is inputted tothe base through a capacitor C, and the output RF signal RF_(out) isoutputted from the collector.

[0186] In the configuration shown in FIG. 10, a choke inductor L forpreventing the RF signal is inserted and connected between the base ofthe bipolar transistor RFTr for RF signal amplification and the emitterof the bipolar transistor Q1. However, it is arbitrary whether the chokeinductor L is provided or not, and it is also possible to remove thechoke inductor L to cause short circuit.

[0187] Further, the resistors R2 and R3 included in the bias currentsupply circuit according to the second embodiment of the invention shownin FIG. 10 also prevent the RF signal from leaking to the bias currentsupply circuit, it is arbitrary whether the resistors R2 and R3 areprovided or not, and it is also possible to remove the resistors R2 andR3 to cause short circuit respectively.

[0188] The circuit including the transistors Q2, Q3, Q4, and Q5 and theresistors R1, R2, and R3 corresponds to the normal temperaturecharacteristic circuit 1 shown in FIG. 9. The circuit including thetransistor Q1 which is of the emitter follower in addition to thecircuit including the transistors Q2, Q3, Q4, and Q5 and the resistorsR1, R2, and R3 forms a bias current supply circuit A having the usualtemperature characteristics.

[0189] Since the bias current supply circuit A has the usual temperaturecharacteristics, the transistor Q1 which is of the emitter followerincreases the base bias current supplied to the bipolar transistor RFTrfor RF signal amplification when the ambient temperature is increased,and the transistor Q1 decreases the base bias current when the ambienttemperature is decreased.

[0190] The transistors Q2, Q3, and Q4 form the current mirror circuitwhich sets the base potential of the transistor Q1. The transistor Q5 isone which sets the current value of the transistor Q1, and the basepotential of the transistor Q5 is supplied from the current mirrorcircuit including the transistors Q2, Q3, and Q4.

[0191] The resistor R1 sets the current value of the transistor Q2, andthe resistors R2 and R3 prevent the RF signal from leaking to the biascurrent supply circuit as described above.

[0192] The control voltage V_(con) determines the collector currents ofthe transistor Q1 and the bipolar transistor RFTr for RF signalamplification, which are supplied from the power supply potential node.

[0193] The circuit including the transistors Q7, Q8, and Q9 and theresistors R4, R5, and R6 corresponds to the bias current compensationcircuit 3 shown in FIG. 9. The circuit including the transistor Q6 inaddition to the circuit including the transistors Q7, Q8, and Q9 and theresistors R4, R5, and R6 forms a bias current compensation circuit D.

[0194] The circuit including the transistors Q7, Q8, and Q9 and theresistors R4, R5, and R6 is one which sets the base potential of thetransistor Q6 which is connected in series to the transistor Q1 and inparallel with the transistor Q5.

[0195] Since each of the bipolar transistors has the normal temperaturecharacteristics, while the emitter current passing through thetransistor Q7 is increased with increasing ambient temperature, theemitter current is decreased with decreasing ambient temperature.Accordingly, while the base potential of the transistor Q6 is increasedwith increasing ambient temperature, the base potential of thetransistor Q6 is decreased with decreasing ambient temperature.

[0196] As a result, the emitter potential of the transistor Q1 which isof the emitter follower is maintained at a relatively higher value whenthe ambient temperature is low, and the emitter potential of thetransistor Q1 is relatively largely decreased when the ambienttemperature is high.

[0197] When the ambient temperature is increased, since the base currentsupplied to the transistor Q1 which is of the emitter follower isincreased, while the emitter current of the transistor Q1 is increased,the base current supplied to the transistor Q6 which is connected inseries to the transistor Q1 and in parallel with the transistor Q5 isalso increased. Consequently, the current passing through the transistorQ6 is increased in the emitter current of the transistor Q1 and becomeslarger than the current passing through the transistor Q5, so that theincrease in bias current supplied from the emitter of the transistor Q1is suppressed.

[0198] On the contrary, when the ambient temperature is decreased, sincethe base current supplied to the transistor Q1 is decreased, while theemitter current of the transistor Q1 is decreased, the base currentsupplied to the transistor Q6 is also decreased. Consequently, thecurrent passing through the transistor Q6 is decreased in the emittercurrent of the transistor Q1, the bias current suppression effectperformed by the bias current compensation circuit D substantiallydisappears, and the most part of the emitter current of the bipolartransistor Q1 is supplied as the bias current.

[0199] Accordingly, in the bipolar transistor RFTr for RF signalamplification whose base bias current is supplied by the emitterfollower formed by the bipolar transistor Q1, the fluctuation in basebias current caused by the temperature change is cancelled. As a result,the fluctuation in collector bias current of the bipolar transistor RFTrfor RF signal amplification, which is caused by the temperature change,is suppressed to the minimum.

[0200] Because each of the bias current supply circuit A and the biascurrent compensation circuit D is formed by the combination of thebipolar transistors which are turned on by the one-stage on-voltageVbeon, the low-voltage operation can be realized in the control voltageV_(con) of the bias current supply circuit according to the secondembodiment of the invention.

[0201]FIG. 11 is the graph showing the temperature characteristics ofthe collector bias current of the bipolar transistor for RF signalamplification to the control voltage V_(con) in the case where the biascurrent supply circuit according to the second embodiment of theinvention is used. In FIG. 11, the graphs T1, T2, and T3 show thetemperature characteristics at ambient temperatures 80° C., 30° C., and−20° C. respectively.

[0202] In the bias current supply circuit A included in the bias currentsupply circuit according to the second embodiment of the invention,although some of reference signs or numerals are different, the circuitconfiguration is completely the same as the bias current supply circuitA included in the bias current supply circuit according to the firstembodiment of the invention. Accordingly, in the case where only thebias current supply circuit A in the bias current supply circuitaccording to the second embodiment of the invention is used, the graphsshowing the temperature characteristics of the collector bias current ofthe bipolar transistor for RF signal amplification to the controlvoltage V_(con) are completely the same as the graphs shown in FIG. 8.

[0203] In the measurement of the temperature characteristics, the indiumgallium phosphide/gallium arsenide (InGaP/GaAs) heterojunction bipolartransistor is used as the bipolar transistor, and the forty eightbipolar transistors for RF signal amplification RFTr whose emitter sizeis 4×30 μm are used. In the bias current supply circuit, the eighttransistors Q1 whose emitter size is 4×30 μm are used, each two of thetransistors Q5 and Q6 whose emitter size is 4×30 μm are used, the twotransistors Q7 whose emitter size is 4×10 μm are used, and each of thetransistors Q2, Q3, Q4, Q7, Q8, and Q9 whose emitter size is 4×10 μm isused.

[0204] With respect to a resistance value of each resistor, the resistorR1 is 600Ω, the resistor R2 is 1000Ω, the resistor R3 is 100Ω, theresistor R4 is 600Ω, the resistor R5 is 3000Ω, and the resistor R6 is400Ω.

[0205] The power supply voltage V_(cc) is 3.4V, and the controlvoltageV_(con) is variable in the range of 2.0V to 3.0V. However, eachof the above setting values is set on the assumption that the controlvoltage V_(con) is set to 2.8V.

[0206] As shown in the graphs of FIG. 11, in the case where the biascurrent supply circuit according to the second embodiment of theinvention is used, when the control voltage V_(con) is set to 2.8V, thecollector bias currents of the bipolar transistor for RF signalamplification are 65 mA, 62 mA, and 54 mA at the ambient temperaturesrespectively, and it is found that the collector bias current is changedlittle. Even if the control voltage V_(con) is fluctuated, it is foundthat the fluctuation in collector bias current of the bipolar transistorfor RF signal amplification is suppressed to a relatively small value.

[0207] On the other hand, as shown in the graphs of FIG. 8, in the casewhere only the bias current supply circuit A in the bias current supplycircuit according to the second embodiment of the invention is used,when the control voltage V_(con) is set to 2.8V, the collector biascurrents of the bipolar transistor for RF signal amplification are 75mA, 52 mA, and 30 mA at the ambient temperatures respectively, and it isfound that the collector bias current is largely changed.

[0208] That is to say, it is found that the use of the bias currentsupply circuit according to the second embodiment of the invention cansuppress the fluctuation in collector bias current of the bipolartransistor for RF signal amplification, which is caused by thetemperature change, to the minimum.

[0209]FIG. 12 is the circuit diagram showing the configuration of thebias current supply circuit and the amplification circuit according to athird embodiment of the invention.

[0210] The bias current supply circuit according to the third embodimentof the invention includes a resistor R1 and a bipolar transistor Q1which are sequentially connected in series between the control potentialnode to which the control voltage V_(con) is supplied and the groundpotential node, a bipolar transistor Q2 in which the collector isconnected to the power supply potential node to which the power supplyvoltage V_(cc) is supplied, the base is connected to the collector ofthe transistor Q1, and the emitter is connected to the base of thetransistor Q1, a resistor R3 which is connected between the emitter ofthe transistor Q2 and the ground potential node, a bipolar transistor Q4in which the collector is connected to the power supply potential nodeand the base is commonly connected to the base of the transistor Q1, adiode-connected bipolar transistor Q3 which is connected between theemitter of the transistor Q4 and the ground potential node, and aresistor R2 which is connected between the control potential node andthe connection node of the emitter of the transistor Q4 and thecollector of the transistor Q3. The base bias current of the bipolartransistor RFTr for RF signal amplification is supplied from theconnection node between the emitter of the bipolar transistors Q4 andthe collector of the transistor Q3.

[0211] The amplification circuit includes the bipolar transistor RFTrfor RF signal amplification which is connected between the power supplypotential node and the ground potential node. In the bipolar transistorRFTr for RF signal amplification, the base is connected to theconnection node between the emitter of the transistor Q4 and thecollector of the transistor Q3, the input RF signal RF_(in) is inputtedto the base through a capacitor C, and the output RF signal RF_(out) isoutputted from the collector.

[0212] In the configuration shown in FIG. 12, a choke inductor L forpreventing the RF signal is inserted and connected between the base ofthe bipolar transistor RFTr for RF signal amplification and theconnection node of the emitter of the transistor Q4 and the collector ofthe transistor Q3. However, it is arbitrary whether the choke inductor Lis provided or not, and it is also possible to remove the choke inductorL to cause short circuit.

[0213] The bias current supply circuit according to the third embodimentof the invention is one in which the conventional bias current supplycircuit shown in FIG. 3 is improved. While the transistor Q2 is insertedand connected in series between the resistor R1 and the transistor Q1 inthe conventional bias current supply circuit shown in FIG. 3, thetransistor Q2 is removed from between the resistor R1 and the transistorQ1 in the bias current supply circuit according to the third embodimentof the invention, and the transistor Q2 and the resistor R3 aresequentially connected in series between the power supply potential nodeand the ground potential node.

[0214] In the bias current supply circuit according to the thirdembodiment of the invention, the transistors Q2 and Q4 function as theemitter follower, and the transistor Q1 sets the base potentials of thetransistors Q2 and Q4. During the high output of the amplificationcircuit, the transistor Q4 supplies the base bias current to the bipolartransistor RFTr for RF signal amplification.

[0215] In the bias current supply circuit according to the thirdembodiment of the invention as well as the conventional bias currentsupply circuit, the resistor R2 and the diode-connected bipolartransistor Q3 are used in order that the idle current passes through.

[0216] In the conventional bias current supply circuit, since the twotransistors Q1 and Q2 are connected in series, the currents passingthrough the transistors Q1 and Q2 are determined by currentIcon=(V_(con)−2Vbeon)/2 (Vbeon is on-voltage of transistor) which passesthrough the resistor R1. Accordingly, when the on-voltage Vbeon of thetransistor is fluctuated according to the change in ambient temperature,the fluctuation is doubled and reflected in the fluctuation in currentIcon, and the current Icon is largely fluctuated. For example, assumingthat the on-voltage Vbeon of the transistor is fluctuated from 1.2V to1.3V according to the change in ambient temperature when the controlvoltage V_(con) is set to 2.8V, the amount of fluctuation in on-voltageVbeon of the two-stage transistors becomes 0.1V+0.1V=0.2V, and thecurrent Icon is largely fluctuated from 0.66 mA to 0.33 mA. As a result,the current value of the transistor Q4 which is of the emitter followeris largely decreased under the influence of the temperature change, andthe amount of supply of the base bias current to the bipolar transistorRFTr for RF signal amplification is also decreased.

[0217] On the other hand, in the bias current supply circuit accordingto the third embodiment of the invention, the resistor R1 and thetransistor Q1 which are sequentially connected in series and thetransistor Q2 and the resistor R3 which are sequentially connected inseries form the circuits in parallel with each other. Accordingly, evenif the on-voltage Vbeon of the transistor is fluctuated according to thechange in ambient temperature, only the amount of fluctuation inon-voltage Vbeon of the one transistor Q1 is reflected in thefluctuation in current Icon passing through the resistor R1, andconstant-current characteristic of the transistor Q2 is maintained bythe resistor R3. As a result, the fluctuation in current value of thetransistor Q4 which is of the emitter follower is suppressed to a smallvalue, and the fluctuation in base bias current supplied to the bipolartransistor RFTr for RF signal amplification is also suppressed to asmall value.

[0218]FIG. 13 is the graph showing the temperature characteristics ofthe collector bias current of the bipolar transistor for RF signalamplification to the control voltage V_(con) in the case where the biascurrent supply circuit according to the third embodiment of theinvention is used. In FIG. 13, the graphs T1, T2, and T3 show thetemperature characteristics at ambient temperatures 90° C., 30° C., and−30° C. respectively.

[0219] In the measurement of the temperature characteristics, the indiumgallium phosphide/gallium arsenide (InGaP/GaAs) heterojunction bipolartransistor is used as the bipolar transistor, and the forty eightbipolar transistors for RF signal amplification RFTr whose emitter sizeis 4×30 μm are used. In the bias current supply circuit, each one of thetransistors Q1 and Q2 whose emitter size is 4×10 μm are used, the onetransistor Q3 whose emitter size is 4×20 μm is used, and the eighttransistors Q4 whose emitter size is 4×30 μm are used.

[0220] With respect to a resistance value of each resistor, the resistorR1 is 600Ω, the resistor R2 is 5000Ω, and the resistor R3 is 3000Ω.

[0221] The power supply voltage V_(cc) is 3.4V, and the controlvoltageV_(con) is variable in the range of 1.4V to 3.0V. However, eachof the above setting values is set on the assumption that the controlvoltage V_(con) is set to 2.8V.

[0222] As shown in the graphs of FIG. 13, in the case where the biascurrent supply circuit according to the third embodiment of theinvention is used, when the control voltage V_(con) is set to 2.8V, thecollector bias currents of the bipolar transistor for RF signalamplification are 39 mA, 35 mA, and 30 mA at the ambient temperaturesrespectively, and it is found that the fluctuation in collector biascurrent is suppressed to a very small value.

[0223] On the other hand, as shown in the graphs of FIG. 4, in the casewhere the conventional bias current supply circuit shown in FIG. 3 isused, when the control voltage V_(con) is set to 2.8V, the collectorbias currents of the bipolar transistor for RF signal amplification are45 mA, 35 mA, and 27 mA at the ambient temperatures respectively, and itis found that the collector bias current is largely changed.

[0224] That is to say, it is found that the use of the bias currentsupply circuit according to the third embodiment of the invention cansuppress the fluctuation in collector bias current of the bipolartransistor for RF signal amplification, which is caused by thetemperature change, to the minimum.

[0225]FIG. 14 is the circuit diagram showing the configuration of amodification of the bias current supply circuits and the amplificationcircuits according to the third embodiment of the invention.

[0226] The modification of the bias current supply circuit according tothe third embodiment of the invention differs from the bias currentsupply circuit according to the third embodiment of the invention shownin FIG. 12 in that the modification further includes a resistor Rc1which is inserted and connected between the base and the collector ofthe transistor Q3 and a resistor Rc2 which is inserted and connectedbetween the base of the transistor Q2 and the collector of thetransistor Q1.

[0227] In the case where the setting values of each transistor, eachresistor, the power supply voltage V_(cc), and the control voltageV_(con) are set as written in the description of FIG. 13, it is preferto set the resistance values of the resistors Rc1 and Rc2 to 1000Ωrespectively.

[0228] By inserting and connecting the resistors Rc1 and Rc2, while thetemperature characteristics shown in the graph of FIG. 13 are realized,the output impedance of the bias current supply circuit becomes low at alow frequency and the output impedance becomes high at a high frequency,so that the choke inductor L for preventing the RF signal is notrequired. Even if the resistors Rc1 and Rc2 are inserted and connected,from the viewpoint of direct current, the temperature characteristics ofthe bias current is substantially equal to the temperaturecharacteristics shown in FIG. 13, as long as the current gain is morethan 100.

[0229] The prevention of the RF signal by the resistors Rc1 and Rc2 isthe effect utilizing beta frequency characteristics of the transistor.From the view point of direct current, the resistors Rc1 and Rc2 onlyshow the resistors in series of about 10Ω. However, from the view pointof alternate current in the range of a radio frequency (RF) , theresistors Rc1 and Rc2 show the resistors in series more than 100Ω, sothat the effect of the prevention of the RF signal can be obtained.

[0230] The basic configuration of the bias current supply circuit andthe amplification circuit according to the first embodiment of theinvention includes the first and second bipolar transistors which formthe two emitter followers cooperating to supply the base bias current ofthe bipolar transistor for signal amplification, the normal temperaturecharacteristic circuit which has the normal temperature characteristicsincreasing the amount of current supply with increasing temperature andsupplies the base current to the first bipolar transistor, and thereverse temperature characteristic circuit which has the reversetemperature characteristics decreasing the amount of current supply withincreasing temperature and supplies the base current to the secondbipolar transistor. As a result, the fluctuation in collector currentcaused by the temperature change can be suppressed in the linearhigh-efficiency, high-power amplification circuit which is operated bylow power supply voltage.

[0231] The basic configuration of the bias current supply circuit andthe amplification circuit according to the second embodiment of theinvention includes the first bipolar transistors which forms the emitterfollower supplying the base bias current of the bipolar transistor forsignal amplification, the second bipolar transistor which is connectedin series to the first bipolar transistor, the normal temperaturecharacteristic circuit which has the normal temperature characteristicsincreasing the amount of current supply with increasing temperature andsupplies the base current to the first bipolar transistor, and the biascurrent compensation circuit which has the normal temperaturecharacteristics increasing the amount of current supply with increasingtemperature and suppresses the increase in base bias current withincreasing ambient temperature by supplying the base current to thesecond bipolar transistor to pass a part of the base bias currentsupplied from the emitter of the first bipolar transistor through thesecond bipolar transistor. As a result, the fluctuation in collectorcurrent caused by the temperature change can be suppressed in the linearhigh-efficiency, high-power amplification circuit which is operated bylow power supply voltage.

[0232] The bias current supply circuit and the amplification circuitaccording to the third embodiment of the invention include the firstresistor and the first bipolar transistor which are sequentiallyconnected in series between the control potential node and the groundpotential node, the second bipolar transistor in which the collector isconnected to the power supply potential node, the base is connected tothe collector of the first bipolar transistor, and the emitter isconnected to the base of the first bipolar transistor, the secondresistor which is connected between the emitter of the second bipolartransistor and the ground potential node, the third bipolar transistorin which the collector is connected to the power supply potential node,the base is commonly connected to the base of the first bipolartransistor, and the emitter supplies the base bias current of thebipolar transistor for signal amplification, the diode-connected bipolartransistor which is connected between the emitter of the third bipolartransistor and the ground potential node, and the third resistor whichis connected between the control potential node and the connection nodeof the emitter of the third bipolar transistor and the collector of thediode-connected bipolar transistor. As a result, the fluctuation incollector current caused by the temperature change can be suppressed inthe linear high-efficiency, high-power amplification circuit which isoperated by low power supply voltage.

What is claimed is:
 1. A bias current supply circuit comprising: a firstbipolar transistor and a second bipolar transistor which form twoemitter followers cooperating to supply a base bias current of a bipolartransistor for signal amplification; a normal temperature characteristiccircuit which has normal temperature characteristics increasing anamount of current supply with increasing temperature and supplies a basecurrent to said first bipolar transistor; and a reverse temperaturecharacteristic circuit which has reverse temperature characteristicsdecreasing the amount of current supply with increasing temperature andsupplies a base current to said second bipolar transistor.
 2. A biascurrent supply circuit comprising: a first bipolar transistor and aresistor which are sequentially connected in series between a powersupply potential node and a ground potential node; a second bipolartransistor which is connected in parallel with said first bipolartransistor; a normal temperature characteristic circuit which has normaltemperature characteristics increasing an amount of current supply withincreasing temperature and is operated by supply of a control voltage tocontrol a base current supplied to said first bipolar transistor; and areverse temperature characteristic circuit which has reverse temperaturecharacteristics decreasing the amount of current supply with increasingtemperature and is operated by the supply of the control voltage tocontrol a base current supplied to said second bipolar transistor,wherein a base bias current of a bipolar transistor for signalamplification is supplied from emitters of said first and second bipolartransistors which are commonly connected.
 3. A bias current supplycircuit comprising: a first bipolar transistor and a second bipolartransistor which are sequentially connected in series between a powersupply potential node and a ground potential node; a third bipolartransistor and a first diode-connected bipolar transistor which aresequentially connected in series between the power supply potential nodeand the ground potential node; a first resistor which is connectedbetween a control potential node and a base of said first bipolartransistor; a fourth bipolar transistor in which a collector isconnected to the base of said first bipolar transistor, a base iscommonly connected to bases of said second bipolar transistor and saidfirst diode-connected bipolar transistor, and an emitter is connected tothe ground potential node; a fifth bipolar transistor which is connectedbetween the power supply potential node and an emitter of said firstbipolar transistor; a second resistor which is connected between thecontrol potential node and a base of said fifth bipolar transistor; athird resistor and a sixth bipolar transistor which are sequentiallyconnected in series between the base of said fifth bipolar transistorand the ground potential node; a seventh bipolar transistor which isconnected between the power supply potential node and a base of saidsixth bipolar transistor; a fourth resistor which is connected betweenan emitter of said seventh bipolar transistor and the ground potentialnode; a fifth resistor which is connected between the control potentialnode and a base of said seventh bipolar transistor; and a seconddiode-connected bipolar transistor and a third diode-connected bipolartransistor which are sequentially connected in series between the baseof said seventh bipolar transistor and the ground potential node.
 4. Abias current supply circuit according to claim 3, further comprising: asixth resistor which is inserted and connected between a base of saidthird bipolar transistor and a connection node of the base of said firstbipolar transistor and said first resistor; and a seventh resistor whichis inserted and connected between the collector of said fourth bipolartransistor and the connection node of the base of said first bipolartransistor and said first resistor.
 5. A bias current supply circuitcomprising: a first bipolar transistor which forms an emitter followersupplying a base bias current of a bipolar transistor for signalamplification; a second bipolar transistor which is connected in seriesto said first bipolar transistor; a normal temperature characteristiccircuit which has normal temperature characteristics increasing anamount of current supply with increasing temperature and supplies a basecurrent to said first bipolar transistor; and a bias currentcompensation circuit which has the normal temperature characteristicsincreasing the amount of current supply with increasing temperature andsuppresses an increase in said base bias current with increasing ambienttemperature by supplying a base current to said second bipolartransistor to pass a part of said base bias current supplied from anemitter of said first bipolar transistor through said second bipolartransistor.
 6. A bias current supply circuit comprising: a first bipolartransistor and a second bipolar transistor which are sequentiallyconnected in series between a power supply potential node and a groundpotential node; a normal temperature characteristic circuit which hasnormal temperature characteristics increasing an amount of currentsupply with increasing temperature and is operated by supply of acontrol voltage to control a base current supplied to said first bipolartransistor; and a bias current compensation circuit which has the normaltemperature characteristics increasing the amount of current supply withincreasing temperature, said bias current compensation circuitcontrolling a base bias current of a bipolar transistor for signalamplification, which is supplied from an emitter of said first bipolartransistor, in such a manner that said bias current compensation circuitis operated by supply of the control voltage to control a base currentsupplied to said second bipolar transistor.
 7. A bias current supplycircuit comprising: a first bipolar transistor and a second bipolartransistor which are sequentially connected in series between a powersupply potential node and a ground potential node; a third bipolartransistor and a first diode-connected bipolar transistor which aresequentially connected in series between the power supply potential nodeand the ground potential node; a first resistor which is connectedbetween a control potential node and a base of said first bipolartransistor; a fourth bipolar transistor in which a collector isconnected to the base of said first bipolar transistor, a base iscommonly connected to bases of said second bipolar transistor and saidfirst diode-connected bipolar transistor, and an emitter is connected tothe ground potential node; a fifth bipolar transistor which is connectedbetween an emitter of said first bipolar transistor and the groundpotential node; a sixth bipolar transistor in which a collector isconnected to the power supply potential node and an emitter is connectedto a base of said fifth bipolar transistor; a second resistor which isconnected between an emitter of said sixth bipolar transistor and theground potential node; a third resistor which is connected between thecontrol potential node and a base of said sixth bipolar transistor; anda fourth resistor, a second diode-connected bipolar transistor, and athird diode-connected bipolar transistor which are sequentiallyconnected in series between the base of said sixth bipolar transistorand the ground potential node.
 8. A bias current supply circuitaccording to claim 7, further comprising: a fifth resistor which isinserted and connected between a base of said third bipolar transistorand a connection node of the base of said first bipolar transistor andsaid first resistor; and a sixth resistor which is inserted andconnected between the collector of said fourth bipolar transistor andthe connection node of the base of said first bipolar transistor andsaid first resistor.
 9. A bias current supply circuit comprising: afirst resistor and a first bipolar transistor which are sequentiallyconnected in series between a control potential node and a groundpotential node; a second bipolar transistor in which a collector isconnected to a power supply potential node, a base is connected to acollector of said first bipolar transistor, and an emitter is connectedto a base of said first bipolar transistor; a second resistor which isconnected between the emitter of said second bipolar transistor and theground potential node; a third bipolar transistor in which a collectoris connected to the power supply potential node, a base is commonlyconnected to the base of said first bipolar transistor, and an emittersupplies a base bias current of a bipolar transistor for signalamplification; a diode-connected bipolar transistor which is connectedbetween the emitter of said third bipolar transistor and the groundpotential node; and a third resistor which is connected between thecontrol potential node and a connection node of the emitter of saidthird bipolar transistor and a collector of said diode-connected bipolartransistor.
 10. A bias current supply circuit according to claim 9,further comprising: a fourth resistor which is inserted and connectedbetween a base and the collector of said diode-connected bipolartransistor; and a fifth resistor which is inserted and connected betweenthe base of said second bipolar transistor and the collector of saidfirst bipolar transistor.
 11. An amplification circuit comprising: afirst bipolar transistor and a second bipolar transistor which form twoemitter followers cooperating to supply a base bias current of a bipolartransistor for signal amplification; a normal temperature characteristiccircuit which has normal temperature characteristics increasing anamount of current supply with increasing temperature and supplies a basecurrent to said first bipolar transistor; a reverse temperaturecharacteristic circuit which has reverse temperature characteristicsdecreasing the amount of current supply with increasing temperature andsupplies a base current to said second bipolar transistor; and thebipolar transistor for signal amplification which is connected between apower supply potential node and a ground potential node, a base of saidbipolar transistor for signal amplification being connected to emittersof said first and second bipolar transistors, an input signal beinginputted to a base of said bipolar transistor for signal amplificationthrough a capacitor, an output signal being outputted from a collectorof said bipolar transistor for signal amplification.
 12. Anamplification circuit according to claim 11, further comprising a chokeinductor which is inserted and connected between the base of saidbipolar transistor for signal amplification and the emitters of saidfirst and second bipolar transistors.
 13. An amplification circuitcomprising: a first bipolar transistor and a resistor which aresequentially connected in series between a power supply potential nodeand a ground potential node; a second bipolar transistor which isconnected in parallel with said first bipolar transistor; a normaltemperature characteristic circuit which has normal temperaturecharacteristics increasing an amount of current supply with increasingtemperature and is operated by supply of a control voltage to control abase current supplied to said first bipolar transistor; a reversetemperature characteristic circuit which has reverse temperaturecharacteristics decreasing the amount of current supply with increasingtemperature and is operated by the supply of said control voltage tocontrol a base current supplied to said second bipolar transistor; and abipolar transistor for signal amplification which is connected betweenthe power supply potential node and the ground potential node, a base ofsaid bipolar transistor for signal amplification being connected toemitters of said first and second bipolar transistors, an input signalbeing inputted to a base of said bipolar transistor for signalamplification through a capacitor, an output signal being outputted froma collector of said bipolar transistor for signal amplification.
 14. Anamplification circuit according to claim 13, further comprising a chokeinductor which is inserted and connected between the base of saidbipolar transistor for signal amplification and the emitters of saidfirst and second bipolar transistors.
 15. An amplification circuitcomprising: a first bipolar transistor and a second bipolar transistorwhich are sequentially connected in series between a power supplypotential node and a ground potential node; a third bipolar transistorand a first diode-connected bipolar transistor which are sequentiallyconnected in series between the power supply potential node and theground potential node; a first resistor which is connected between acontrol potential node and a base of said first bipolar transistor; afourth bipolar transistor in which a collector is connected to the baseof said first bipolar transistor, a base is commonly connected to basesof said second bipolar transistor and said first diode-connected bipolartransistor, and an emitter is connected to the ground potential node; afifth bipolar transistor which is connected between the power supplypotential node and an emitter of said first bipolar transistor; a secondresistor which is connected between the control potential node and abase of said fifth bipolar transistor; a third resistor and a sixthbipolar transistor which are sequentially connected in series betweenthe base of said fifth bipolar transistor and the ground potential node;a seventh bipolar transistor which is connected between the power supplypotential node and a base of said sixth bipolar transistor; a fourthresistor which is connected between an emitter of said seventh bipolartransistor and the ground potential node; a fifth resistor which isconnected between the control potential node and a base of said seventhbipolar transistor; a second diode-connected bipolar transistor and athird diode-connected bipolar transistor which are sequentiallyconnected in series between the base of said seventh bipolar transistorand the ground potential node; and a bipolar transistor for signalamplification which is connected between the power supply potential nodeand the ground potential node, a base of said bipolar transistor forsignal amplification being connected to the emitter of said firstbipolar transistor and an emitter of said fifth bipolar transistor, aninput signal being inputted to the base of said bipolar transistor forsignal amplification through a capacitor, an output signal beingoutputted from an collector of said bipolar transistor for signalamplification.
 16. An amplification circuit according to claim 15,further comprising: a sixth resistor which is inserted and connectedbetween a base of said third bipolar transistor and a connection node ofthe base of said first bipolar transistor and said first resistor; and aseventh resistor which is inserted and connected between a collector ofsaid fourth bipolar transistor and the connection node of the base ofsaid first bipolar transistor and said first resistor.
 17. Anamplification circuit according to claim 15, further comprising a chokeinductor which is inserted and connected between the base of saidbipolar transistor for signal amplification and the emitters of saidfirst and fifth bipolar transistors.
 18. An amplification circuitcomprising: a first bipolar transistor which forms an emitter followersupplying a base bias current of a bipolar transistor for signalamplification; a second bipolar transistor which is connected in seriesto said first bipolar transistor; a normal temperature characteristiccircuit which has normal temperature characteristics increasing anamount of current supply with increasing temperature and supplies a basecurrent to said first bipolar transistor; a bias current compensationcircuit which has the normal temperature characteristics increasing theamount of current supply with increasing temperature and suppresses anincrease said the base bias current with increasing ambient temperatureby supplying a base current to said second bipolar transistor to pass apart of said base bias current supplied from an emitter of said firstbipolar transistor through said second bipolar transistor; and thebipolar transistor for signal amplification which is connected between apower supply potential node and a ground potential node, a base of saidbipolar transistor for signal amplification being connected to theemitter of said first bipolar transistor, an input signal being inputtedto the base of said bipolar transistor for signal amplification througha capacitor, an output signal being outputted from a collector of saidbipolar transistor for signal amplification.
 19. An amplificationcircuit according to claim 18, further comprising a choke inductor whichis inserted and connected between the base of said bipolar transistorfor signal amplification and the emitter of said first bipolartransistors.
 20. An amplification circuit comprising: a first bipolartransistor and a second bipolar transistor which are sequentiallyconnected in series between a power supply potential node and a groundpotential node; a normal temperature characteristic circuit which hasnormal temperature characteristics increasing an amount of currentsupply with increasing temperature and is operated by supply of acontrol voltage to control a base current supplied to said first bipolartransistor; a bias current compensation circuit which has the normaltemperature characteristics increasing the amount of current supply withincreasing temperature, said bias current compensation circuitcontrolling a base bias current of a bipolar transistor for signalamplification, which is supplied from an emitter of said first bipolartransistor, in such a manner that said bias current compensation circuitis operated by supply of the control voltage to control a base currentsupplied to said second bipolar transistor; and the bipolar transistorfor signal amplification which is connected between the power supplypotential node and the ground potential node, a base of said bipolartransistor for signal amplification being connected to the emitter ofsaid first bipolar transistor, an input signal being inputted to thebase of said bipolar transistor for signal amplification through acapacitor, an output signal being outputted from a collector of saidbipolar transistor for signal amplification.
 21. An amplificationcircuit according to claim 20, further comprising a choke inductor whichis inserted and connected between the base of said bipolar transistorfor signal amplification and the emitter of said first bipolartransistors.
 22. An amplification circuit comprising: a first bipolartransistor and a second bipolar transistor which are sequentiallyconnected in series between a power supply potential node and a groundpotential node; a third bipolar transistor and a first diode-connectedbipolar transistor which are sequentially connected in series betweenthe power supply potential node and the ground potential node; a firstresistor which is connected between a control potential node and a baseof said first bipolar transistor; a fourth bipolar transistor in which acollector is connected to the base of said first bipolar transistor, abase is commonly connected to bases of said second bipolar transistorand said first diode-connected bipolar transistor, and an emitter isconnected to the ground potential node; a fifth bipolar transistor whichis connected between. an emitter of said first bipolar transistor andthe ground potential node; a sixth bipolar transistor in which acollector is connected to the power supply potential node and an emitteris connected to a base of said fifth bipolar transistor; a secondresistor which is connected between an emitter of said sixth bipolartransistor and the ground potential node; a third resistor which isconnected between the control potential node and a base of said sixthbipolar transistor; a fourth resistor, a second diode-connected bipolartransistor, and a third diode-connected bipolar transistor which aresequentially connected in series between the base of said sixth bipolartransistor and the ground potential node; and a bipolar transistor forsignal amplification which is connected between the power supplypotential node and the ground potential node, a base of said bipolartransistor for signal amplification being connected to the emitter ofsaid first bipolar transistor, an input signal being inputted to thebase of said bipolar transistor for signal amplification through acapacitor, an output signal being outputted from a collector of saidbipolar transistor for signal amplification.
 23. An amplificationcircuit according to claim 22, further comprising: a fifth resistorwhich is inserted and connected between a base of said third bipolartransistor and a connection node of the base of said first bipolartransistor and said first resistor; and a sixth resistor which isinserted and connected between the collector of said fourth bipolartransistor and the connection node of the base of said first bipolartransistor and said first resistor.
 24. An amplification circuitaccording to claim 22, further comprising a choke inductor which isinserted and connected between the base of said bipolar transistor forsignal amplification and the emitter of said first bipolar transistors.25. An amplification circuit comprising: a first resistor and a firstbipolar transistor which are sequentially connected in series between acontrol potential node and a ground potential node; a second bipolartransistor in which a collector is connected to a power supply potentialnode, a base is connected to a collector of said first bipolartransistor, and an emitter is connected to a base of said first bipolartransistor; a second resistor which is connected between the emitter ofsaid second bipolar transistor and the ground potential node; a thirdbipolar transistor in which a collector is connected to the power supplypotential node, a base is commonly connected to the base of said firstbipolar transistor, and an emitter supplies a base bias current of abipolar transistor for signal amplification; a diode-connected bipolartransistor which is connected between the emitter of said third bipolartransistor and the ground potential node; a third resistor which isconnected between the control potential node and a connection node ofthe emitter of said third bipolar transistor and a collector of saiddiode-connected bipolar transistor; and the bipolar transistor forsignal amplification which is connected between the power supplypotential node and the ground potential node, a base of said bipolartransistor for signal amplification being connected to the emitter ofsaid third bipolar transistor, an input signal being inputted to thebase of said bipolar transistor for signal amplification through acapacitor, an output signal being outputted from a collector of saidbipolar transistor for signal amplification.
 26. An amplificationcircuit according to claim 25, further comprising: a fourth resistorwhich is inserted and connected between a base and the collector of saiddiode-connected bipolar transistor; and a fifth resistor which isinserted and connected between the base of said second bipolartransistor and the collector of said first bipolar transistor.
 27. Anamplification circuit according to claim 25, further comprising a chokeinductor which is inserted and connected between the base of saidbipolar transistor for signal amplification and the emitter of saidthird bipolar transistors.